Restaurants in general generate large amounts of heat and grease-laden exhaust from the frying and broiling of various food items which are prepared. This grease-laden hot exhaust is typically drawn up through a kitchen hood and exhaust duct combination to the atmosphere by a fan arrangement. However, the heat is generally lost up the exhaust duct.
Any attempt to capture and reuse this waste heat runs into problems because energy recovery devices which use heat exchangers have either reduced heat-transfer properties due the grease that deposits on their surfaces, or because the heat extraction process employed to recover this heat is generally not very efficient.